/Engine/Plugins/Runtime/RigVM/Source/RigVMDeveloper/Public/RigVMCompiler/RigVMAST.h
An abstract syntax tree literal expression represents the definition of const memory for a single variable - vs a var expression which is mutable. In C++ the literal expression is a literal declaration, for ex: const float PI = 3.14f; The literal expression references a pin from the model.
class FRigVMLiteralExprAST : public [FRigVMVarExprAST](API\Plugins\RigVMDeveloper\RigVMCompiler\FRigVMVarExprAST)